Improvement in let-off mechanisms



UNITED STATES PATENT OFFICE.

IMPROVEMENT IN LET-OFF MECHANISMS.

Specification forming part of Letters Patent No. 117,779, dated August 8, 1871.

To all whom t't may concern:

Be it known that I, WILLIAM H. HOWARD, of Philadelphia, coimty of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Let-off Motions for Looms and I do hereby declare that the following is a full, clear, and exact description of the saine, reference being had to the annexed drawing, of which- Figure l is a perspective view of the apparatus, and Fig. 2 an end view, showing the device in its two extreme positions.

My invention relates to that class of let-od' motion in which the mechanism is so arranged that it will automatically keep the warp-threads at the same tension, whether they are unwound from a full or empty beam.

The common practice is to pass ropes or straps over the heads b b, which are fastened to each end of the yarn-beam s, and between which the yarn c is wound. To these straps levers are attached, 011 which usually a weightis hung, which the attendant moves on the lever according to the tension required. Suppose the beam has been filled with yarn to the line c c a, Fig. 2, a certain pressure is required upon the heads b to keep the warp-threads at the proper tension; now, with every revolution of the beam or with every convolution of yarn wound oii", the threads unwind nearer to the center s ofthe beam, while the point of pressure upon the beam-heads b b remains constant, so that in order to keep the tension constantly the same the pressure must be reduced.

This is accomplished in my invention by causing the lever g, to which the weight w is hung,

to change its angular position in such a manner that, when thebeam is full of yarn, it shall act upon the head b with greater force than when the beam is empty, and the reduction of this force shall be proportionate to the reduction of the diameter of the coils of yarn on the beam. For this purpose the shaft c is provided, upon which the arm h can oscillate freely. rIhe extremity of this arm has a iiat circular surface, which bears against the yarn a.. To the lower part of L is attached the strap c, which passes around the beam-head Y b, and whose other end is fastened to the pulley j', which, in turn, is rigidly attached to the shaft e. This shaft c oscillates freely in bearings o 0, and carries upon its outer extremity the lever g, to which the weight fw is hung. When the beam s, Fig. 2, is full of yarn the lever g is intended to be in a horizontal position, as shown by full lines, Fig. 2, and the weight w is moved either toward or from the fulerum of the lever until the right amount of tension is obtained. As the quantity of yarn on s diminishes, the lever-arm h oscilla-tes toward the 'center-of s. By this motion it allows the strap c to become slack, but the latter is taken up immediately by the weighted vlever g. In taking up this slack, however, the lever g has to descend, whereby its effect upon the strap is diminished. Suppose the empty beam s, whose periphery is represented by d d d, is six inches diameter, and the circle c c a, which represents the periphery of the yarn, when the maximum quantity has been wound on, is twelve inches diameter, then the different leverages between h and g must be so proportioned that the lever g will move from a horizontal position through an are, a' w, of sixty degrees, while the arm h moves from its outer position to its inner one, as shown by dotted lines, because at w the elfect of the weight w has been reduced one-half, and the diameters of the coils of yarn from a a c to d d el have also been reduced one-half, so that the tension will be constant.

I claim- The arrangement of the shaft e, armk, strap c, pulley f, and weighted lever g, when combined as herein described, with the beam s.

W. H. HOWARD.

Witnesses:

J. P. DELANEY, PHILIP J. TAYLOR. 

